Growing Eggplants

Growing Eggplants

​Eggplants (Solanum melongena), also known as aubergines, are in the nightshade family (Solanaceae) along with tomatoes, peppers, and potatoes. The most well-known eggplants have the scientific name of Solanum melongena, although another less common species is S. aethiopicum (also known as S. integrifolium or S. gilo depending on where the eggplant originates). S. aethoiopicum is also called Ethiopian eggplant, bitter tomato, because they often look like a cross between a ripe tomato and an eggplant, or Pumpkin on a Stick, because some varieties look like miniature pumpkins. For more information on eggplant varieties, including their days to maturity, color and shape, origin, and more, please see my previous blog post.

Eggplants are used as vegetables, even though they are technically fruits, similar to tomatoes and peppers. The most popular eggplant varieties in the United States are dark purple, bell-shaped fruits that are Italian eggplant cultivars. Elongated purple fruits also exist, usually of Asian descent, coming from Japan, China, Thailand, and India. However small, round eggplants, mini bell-shaped or elongated fruits, and those of various colors, including white, green, striped, and orange, also exist.

Growing Conditions

​Eggplants, like tomatoes and peppers, prefer long, hot summers, although they grow quite well in northern climates by starting seeds early or buying transplants. Some newer hybrids have shorter days to maturity, but most eggplants need 60-90 days after transplanting to fully mature. If you are unfamiliar with starting plants from seed, please see my earlier blog post on “Starting Seeds.” Start seeds 6-10 weeks before transplanting outside, preferably on a heat mat. Seeds germinate at 80-90°F and grow best at 70°F after the seedlings emerge. Harden off the plants by reducing the temperature and exposing them to partial sun and wind. Once fully hardened off, transplant them into a raised bed or in-ground garden. I usually transplant my starts about 2 weeks after my average last frost date, usually the end of May to the beginning of June. If it is still cooler when transplanting, the plants will benefit from a frost cover. This will also keep insects at bay. The cover will need to be removed once the plant blossoms so pollination can occur (unless you are growing a parthenocarpic variety, which does not require pollination to set fruit. Space plants 18-24” inches apart in rows 30-36 inches apart. Because I grow my eggplants in raised beds, I do not use rows and instead plant them about 18” apart, sometimes going as small as 12”. This works okay for me because I keep my soil amended with compost and composted manure, so there are plenty of nutrients for the plants.

​Eggplants require fertile soil that is well-drained. Similar to other Solanum plants, they do not like wet feet. I always grow my eggplants in raised beds to ensure the best quality soil and proper drainage. If you are going to use chemical fertilizer, make sure it does not contain too much nitrogen, as this will encourage vegetative growth but not fruit set. A fertilizer designed for peppers and tomatoes also works well for eggplants. Many eggplant varieties are prolific enough that staking the plants is helpful. Some varieties are also more compact, so they do well in containers. Most varieties of eggplants do not grow bigger than about 2-3 feet tall and will still do well in containers.

Pests and Disease

​Eggplants are fairly disease and pest hardy, but flea beetles can be a problem, particularly when the plants are small. Colorado potato beetles also like eggplant, although not as much as potato plants. These bugs are easy to pick off but also check for orange eggs on the underside of the leaves and remove those as well. I have problems with slugs eating the fruit wherever it touches the ground. Staking the plants to keep most of the fruit off the ground is helpful. Lastly, I occasionally have aphid problems. Usually, spraying them off with strong hose water is sufficient to keep them at bay. One year I had such a problem with aphids I eventually pulled the plant because the aphids kept returning whether I sprayed them with water or even insecticidal soap. Eggplants can also be susceptible to diseases, such as Verticillium wilt. Rotating crops as much as possible can help reduce the incidence of disease. Some eggplant varieties are also disease-resistant.

Harvest and Usage

​Once mature, harvest the eggplant regularly, and the plant will continue to set more fruit. Eggplants are mature when the fruit is glossy, and the flesh yields slightly when pressed. If over-mature, the fruit can become bitter and seedy. If the eggplant has lost its shine, it is overripe. Eggplant is usually cooked, but some varieties can be eaten raw. Eggplants are commonly used in Italian cooking, such as Eggplant parmesan, in Asian cooking, in stir-fries and curries, and in Mediterranean cooking, such as Greek Moussaka. Eggplant generally cannot be canned, although Ball has a recipe for eggplant puttanesca (found in “The All New Ball Book of Canning and Preserving”), which is quite good. You can freeze eggplant after slicing it into 1/3-inch pieces and blanching for approximately four minutes in water containing ½ cup lemon juice per gallon of water. The lemon juice helps prevent the flesh from oxidizing and turning dark-colored.

Conclusion

​Although eggplants are not my favorite to eat, I do enjoy eggplant parmesan a few times per year. I always grow at least one Italian-type and one Asian-type each season. Compared to tomatoes, they are much more disease-resistant, are lower maintenance, and take up less space in the garden.

References and Resources

1. Cox, Jeff. 1988. How to Grow Vegetables Organically. Rodale’s Organic Gardening Magazine, Rodale Press, Emmaus, Pennsylvania.
2. Disease-resistant eggplant varieties. Cornell Vegetables Resources for commercial growers. Cornell CALS College of Agriculture and Life Sciences. https://www.vegetables.cornell.edu/pest-management/disease-factsheets/disease-resistant-vegetable-varieties/disease-resistant-eggplant-varieties/
3. Eggplant – Key Growing Information. Johnny’s Selected Seeds. https://www.johnnyseeds.com/growers-library/vegetables/eggplant/eggplant-key-growing-information.html
4. Michigan Fresh: Using, Storing, and Preserving Eggplant. Michigan State University. MSU Extension. https://www.canr.msu.edu/resources/michigan_fresh_eggplant